2018 06 29.577 UT
Discovered by Y. Sakurai, Mito, Japan, on two frames using Nikon D7100 digital camera + 180-mm f/2.8 lens, who writes there is a variable star TSVSC1-TN-S300112300-126-67-2 at 21s.88 and 51".1. Nothing is visible at this location on a frame (limit mag.= 12.1) taken on 2018 June 23.632 UT.

Here is a light curve done last night over 3:15 hours. This is a relative measurement. Olivier Garde advised me to seek for other light curves. So, I am posting just in case it may be interesting for anyone here.